GENETIC

INHERITANCE

subtopi

cs

Mendelian

Genetics

(C1)

Deviations From The

Mendelian Inheritance

(C1)

Genetic

Mapping

(C1)

4.1

4.2

4.3

Learning

outcomes

4.1: Mendelian Gene

a)Define the terminologies

b)State the characteristics of Mandel’s pea plants

c)State Mendel’s first law

d)State Mendel’s second law

4.2: Deviations from the Mendelian Inheritance

- Define types of inheritance that deviate from

Mendelian

4.3: Genetic Mapping

- Define genetic mapping

Deviations from the

Mendelian inheritance

Codominant alleles

Incomplete

dominant alleles

Multiple alleles

Linked genes

sex-linked genes

polygenes

Both alleles of a

pair are fully

expressed in a

heterozygote.

Codominant Allele

Roan coat color:

Both alleles are

equally expressed

in the heterozygot

A form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele.

Incomplete dominant

allele

Snapdragons show incomplete dominance in the inheritance of

flower color. The heterozygous flower has a phenotype that is in

between that of the two homozygotes

MORE THAN TWOalleles control forparticular trait OF ACHARACTER

Multiple allele

Coat Color in Rabbits Different combinations of two

alleles give different coat colors and pigment distributions.

Each chromosome carries a number of genes in

particular locus

Linked gene

Genes that are

carried by either

sex chromosomes

( X or Y) are said to

be Sex-Linked

Sex- Linked gene

An additive effect of TWO or

MORE genes on a single

phenotypic character

Eg; skin colour, body height

Polygene

GENETIC MAPPING

Polygene• Genetic map - A graphic representation of the arrangement

of a gene or a DNA sequence on a chromosome.

GENETIC MAPPING

Polygene

• genetic mapping - Process of locating the relative

position & sequence of gene on a chromosome.

• Can be carried out when the genes are linked and

crossing over has taken place

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